Method of holding work



Nov. 23, 1965 R..W. WARlNG 3,219,888

METHOD OF HOLDING WQRK Filed June 20, 1961 INVENTOR. ROBERT W. WARING ATTORNEY United States Patent 3,219,888 METHOD OF HOLDING WORK Robert W. Waring, 197 Old Post Road, Fairfield, Conn. Filed June 20, 1961, Ser. No. 118,458 4 Claims. (Cl. 317--162) The present invention relates to a method of holding work on a platen in a manner to perform operations thereon, and particularly to a new and improved method of holding work having surfaces that contact the platen and which surfaces are of too small area to produce sufficient attractive forces between said areas and said platen.

It often becomes necessary to hold work onto a platen while operations are being performed thereon wherein the work includes relatively small areas in contact with the platen and possesses relatively large projected areas normal to the platen. One example, by way of illustration only, is the machining of material of honeycomb structure such as stainless steel honeycomb material in which it is desired to machine the structure to a predetermined thickness within relatively close tolerances. Supporting such material on a platen with the passages normal to the platen surfaces results in such small areas being in contact with the platen that they fail to respond sulficiently if the material is magnetic or non-magnetic metal, to magnetic or electrostatic holding forces; and if of nonmetallic construction, to any attractive forces.

The principal object of the invention is to provide a method of holding work to a platen when the contact area between the work and platen is insufficient to produce adequate attractive forces between said contact area and said platen.

Another object of the invention is to provide such a method of holding such work in which the contact area between the work and platen is insuflicient to respond, if such work is magnetic or non-magnetic metal, to magnetic or electrostatic forces.

Another object of the invention is to provide such a method of holding such work in which the work can be readily applied to and removed from the platen.

Still another object of the invention is to provide such a method of holding such work in which the holding forces are applied to the projected areas of the work normal to the platen surface.

In one aspect of the invention, the work, which may be magnetic, non-magnetic metal or even non-metallic, may be partially immersed within a fluid vehicle having suspended therein magnetizable particles, which fluid may then be referred to as a magnetizable fluid. The magnetizable fluid may be confined on the platen surface and may be subjected to a magnetic field originating in the platen. It has been found that a piece of stainless steel honeycomb may be placed on a platen which confines a body of magnetizable fluid on its surface in such a manner that the through passages of the honeycomb are normal to the platen surface. By forcing the entire bottom face of the honeycomb into contact with the platen, a substantial portion of the surfaces of the honeycomb normal to the platen surface is partially immersed within the magnetizable fluid. Then, by subjecting the magnetizable fluid to a magnetic field, the honeycomb is held in intimate contact with the platen surface with a force preventing its movement either away from the platen surface or in a direction parallel to the platen surface, and such force is of suflicient intensity to permit application of metal working operations on the honeycomb construction.

It can be theorized that the magnetizable particles within the fluid are acted upon by the magnetic field and become an extension of the main magnetic poles, so that the magnetizable particles on opposite sides of the surfaces 3,219,888 Patented Nov. 23, 1965 ice of the honeycomb that are normal to the platen surface attract each other and therefore apply a force of considerable intensity to opposite faces of said honeycomb surfaces.

The above, other objects and novel features of the invention will become apparent from the following specification and accompanying drawing which is merely exemplary.

In the drawing:

The figure is a part sectional elevational view of apparatus to which the principles of the invention have been applied.

Referring to the drawing, the principles of the invention have been shown as applied to a multi-poled electromagnetic chuck 10 having a base 11 and iron pole pieces 12 and 13 separated by non-magnetic insulation 14. Poles 13 are surrounded by coils 15 which are connected by conductors 16 and 17 through switch 18 to a source of direct current power 19. Closing switch 18 will produce magnetic flux lines passing from poles 13 through base 11 upward through poles 12, resulting in alternate north and south poles appearing at the upper faces of poles 12 and 13,.respectively. The chuck 10 may include an upstanding flange 20 around its periphery, and a magnetizable fluid 21 may be confined within the flange and upon the supporting surface of the chuck 10. Although any fluid such as oil, water or even air, may act as the vehicle, a chlorinated biphenyl or polyphenyl, sold under the trade name of Aroclor 1248 was found to produce excellent results.

The magnetizable fluid may comprise any vehicle in Which may be suspended magnetizable particles. The magnetizable particles may also be of different forms, size and composition. However, a carbonyl iron powder having an average particle diameter of 10 microns and a range of 3 to 17 microns has been employed. While the quantity of iron particles may vary widely, it was found that 2.00 per-cent by weight of powder added to the weight of Aroclor 1248 vehicle produced excellent results. In order to assist in the dispersion of the iron powder within the vehicle, a smalltamount of a dispersing agent, Emulphor EL-620, was added to the vehicle. The vehicle with the dispersing agent and iron powder was placed in a ball mill to ensure thorough dispersion of the iron powder within the vehicle. The magnetizable fluid 21 is then poured onto the chuck surface 22 within the confines of a flange 20 to be predetermined level. A work piece, which in the embodiment disclosed is shown as a member 23 of cellular honeycomb construction having walls 24, may be placed in the fluid bath 21 and forced downwardly therethrough so that its entire bottom face contacts the chuck surface 22. Upon closing switch 18, magnetic flux lines 25 are formed above the ends of adjacent north and south poles 12 and 13, passing through fluid 21. The fluid 21 rigidifies as the magnetizable particles line up from the flux and hold work 23, preventing it from moving away from surface 22 and also preventing its motion sideways over surface 22.

It can be theorized that the lines of force 25 coming from each pole 12, 13 move upwardly in a roughly semielliptical fashion, through the cell walls 24 and downwardly to the surface of the next adjacent pole of opposite polarity. In so doing, these force lines probably make quarter-elliptical shaped flux paths coming to each side of every cell wall 24 which does not fall directly on the middle of one of the poles 12, 13. The rigidified fluid 21, therefore, is not only held to the surface 22 but also held to the adjacent sides of each cell wall, thereby in effect clamping the work 23 to the chuck surface 22. In effect, the north and south poles appearing at the surface of pole pieces 12 and 13 are extended through the magnetic Such a system is immune to the use of water as coolant, or even an electrolyte in processes Where an electrolyte is employed in the work machining operation, particularly if the vehicle of the magnetizable fluid is of greater density than that of water or the electrolyte.

After the machining operation, the coolant water and/ or the electrolyte may be removed by draining or otherwise, prior to opening switch 18 when a de-rnagnetizing means may be employed. This causes the rigidified magnetizable fluid to become fluid so that the machined work may be removed from the chuck whereupon the fluid drains from the work.

Although the various features of the new and improved method have been shown and described in detail to fully disclose one embodiment of the invention, it will be evident that changes may be made in such details and certain features may be used without others without departing from the principles of the invention.

What is claimed is:

1. The method of holding work onto a chuck having a work-supporting surface for performing operations thereon which comprises confining on said work-supporting surface a magnetizable fluid to a depth less than the thickness of the work to be machined; forcing a work piece through said fluid so that its surface opposite that to be machined is in intimate contact with said work-supporting surface of said chuck; and subjecting said magnetizable fluid to a magnetic field of such intensity that said magnetizable fluid is rigidified and holds said work to the work-supporting surface of said chuck.

2. The method of holding work onto a chuck having a work-supporting surface for performing operations thereon which comprises confining on said work-supporting surface a magnetiz-able fluid to a depth less than the thickness of the work to be machined, said fluid comprising a vehicle and iron particles; forcing a work piece through said fluid so that its surface opposite that to be machined is in intimate contact with said work-supporting surface of said chuck; and subjecting said magnetizable fluid to a magnetic field of such intensity that said magnetizable fluid is rigidified and holds said work to the work-supporting surface of said chuck.

3. The method of holding Work onto a chuck having a work-supporting surface for performing operations thereon which comprises confining on said work-supporting surface a magnetizable fluid composed of a vehicle immiscible with an aqueous solution to a depth less than the thickness of the work to be machined; forcing a work piece through said fluid so that its surface opposite that to be machined is in intimate contact with said worksupporting surface of said chuck; and subjecting said magnetizable fluid to a magnetic field of such intensity that said magnetizable fluid is rigidified and holds said work to the work-supporting surface of said chuck.

4. The method of holding work onto a chuck having a work-supporting surface for performing operations on said work involving the use of an electrolyte which comprises confining on said work-supporting surface a magnetizable fluid composed of a vehicle having a density greater than said electrolyte to a depth less than the thickness of the work to be machined; forcing a work piece through said fluid so that its surface opposite that to be machined is in intimate contact with said work-supporting surface of said chuck; and subjecting said magnetizable fluid to a magnetic field of such intensity that said magnetizable fluid is rigidified and holds said work to the worksupporting surface of said chuck.

References Cited by the Examiner UNITED STATES PATENTS 2,650,684 9/1953 English 317-201 2,744,409 5/ 1956 Wintle et al 192--21 2,999,275 9/1961 Blume 317-203 BERNARD A. GILHEANY, Primary Examiner.

SAMUEL BERNSTEIN, JOHN F. BURNS, LARAMIE E. ASKIN, Examiners. 

1. THE METHOD OF HOLDING WORK ONTO A CHUCK HAVING A WORK-SUPPORTING SURFACE FOR PERFORMING OPERATIONS THEREON WHICH COMPRISES CONFINING ON SAID WORK-SUPPORTING SURFACE A MAGNETIZABLE FLUID TO A DEPTH LESS THAN THE THICKNESS OF THE WORK TO BE MACHINED; FORCING A WORK PIECE THROUGH SAID FLUID SO THAT ITS SURFACE OPPOSITE THAT TO BE MACHINED IS IN INTIMATE CONTACT WITH SAID WORK-SUP- 